1. Field of the Invention
The present invention relates, in general, to speed detection of moving vehicles, and more particularly to compact, mobile speed detection systems that provide for accurate speed detection with accompanying image capture, processing, and production at the location of the field portion of the system, such as the present location of the law enforcement vehicle.
2. Relevant Background
Law enforcement agencies and personnel presently use a variety of speed measurement devices to monitor traffic and, more particularly, to identify vehicles that are going faster than posted speed limits. In addition to identifying a speeding vehicle, it has become increasingly common to attempt to capture images of such speeding vehicles and then to use the images to better enforce the speed limits (i.e., use the image as part of a ticketing program). While satisfying some of the needs of the law enforcement agencies, the existing speed measurement and image capture devices have not proven suitable or reliable for many law enforcement agency applications and have created operational problems that hinder the field use of such devices.
Various methods are used to detect the speed of moving vehicles, such as well-known radar systems. More recently, speed detection systems have incorporated lasers to accurately detect the speed of a moving vehicle and also the distance or range of the vehicle from the laser device. In general, laser speed detectors measure the time delay between the transmission of a series of pulses and a reflection of those pulses. The design and operation of laser speed detection and range finder systems may be found in U.S. Pat. No. 5,359,404 entitled “Laser-Based Speed Measuring Device, U.S. Pat. No. 5,652,651 entitled “Laser Range Finder Having Selectable Target Acquisition Characteristics and Range Measuring Precision”, and U.S. Pat. No. 6,057,910 entitled “Self-Calibrating Precision Timing Circuit and Method for Laser Range Finder”, which are each incorporated herein by reference. Typically, these laser speed detection systems provide accurate measures of a vehicle's speed and are useful for providing onsite speed measurements, e.g., at the location of a law enforcement vehicle, that could then be entered on a ticket by law enforcement personnel.
Improvements have been made to increase the accuracy and usefulness of these laser-based speed detection systems. For example, U.S. Pat. No. 5,938,717 entitled “Speed Detection and Image Capture System for Moving Vehicles”, which is incorporated herein by reference, discloses a system for accurately aligning a laser speed detector and for capturing an image of a speeding vehicle with a video camera. The system also provides the advantage of automating the capture of images of speeding vehicles at a predetermined distance from the system and of capturing a set of useful information (e.g., date, time, location, speed limit, detected speed, and the like). A computer system is included in the disclosed system to run a frame grabber program to capture a frame of the video image. The computer system includes a removable data storage device for storing the captured image frames and the associated set of information.
Generally, the system is taught to be operated by placing the system in a selected location to monitor vehicle speeds, such as along a road with the bulky computer system position in the back of a van or other vehicle. The system is initially set up by an operator and then allowed to operate automatically without or with minimal operator control for a certain period of time. An operator then removes the data storage device from the system and takes the data storage device back to a separate office or facility for processing of the captured images (i.e., grabbing a still image from the video) and data with a computer system at the office. In this manner, tickets can be produced by combining the video image with the collected data and then mailing the ticket to owners of vehicles that violated a speed limit by a selected amount (such as 5 miles per hour in a school zone and 10 miles per hour for a highway). A hardcopy of the image may be included with the ticket with the data being overlaid by the office computer system. In some applications, the field computer system, such as a personal computer, includes a monitor to allow an operator to view the collected image and to facilitate entering of field parameters. Additionally, the field computer system may perform some of the processing features (such as overlaying of the set of information on a grabbed frame of the video) and may include a thermal printer to produce copies of the image with the overlaid information at the field unit.
While addressing some of the needs of law enforcement agencies, the video-based laser speed detection systems have not addressed all of the operating problems facing field operators and are not particularly useful in some field applications. For example, the use of frame grabbing with a video camera for image capturing is most effective with-a relatively high capacity and higher speed data processing system and large data storage capacity. Typically, the computer requirements are met with a personal computer with central processing unit with a frame grabber PC card installed and associated monitor and keyboard. The combined use of a video camera with a personal computer results in a bulky package that is often costly and is usually physically large, which limits its usefulness in the field. It is not convenient or even practical for a single operator, i.e., law enforcement officer, to quickly deploy the system and then periodically move the entire system or portions of the system without moving the whole vehicle in which the system is positioned. The portability of these video-based systems is further limited by the need for a large number of communication cables and power cords (e.g., generally AC and DC power provided to each component) between the various components.
One of the most significant advantages of a laser-based speed measurement instrument is its ability to narrowly target a single car within a group of cars. However, there is still a need for proof that the detected speed is matched with the correct car. This proof can be provided with the overlaid information if it is accurately synchronized with the proper, grabbed video frame. Of course, this synchronization and combining of information requires additional processing capacity that increases the cost and sometimes the size of the system. Also, the time required to process the information and to print out a hard copy of the produced image limits its desirability as evidence or proof of speeding in the field as enforcement officers demand relatively quick evidential support to be used during the issuance of a speeding ticket.
Hence, there remains a need for a device or system for detecting a speed of a moving vehicle and for capturing an image of the vehicle that provides an accurate determination of the vehicle's speed along with readily accessible proof that the speed has been correctly matched to the proper vehicle. Preferably, such a speed measurement device would be designed for field use (such as inside or outside an operator's vehicle) providing prompt and useful evidence of a vehicle's speed while also being compact, lightweight, and easy to operate. The device would also preferably be useful in various weather conditions, provide protection of collected images and data, and be relatively inexpensive to purchase and operate.